Flight control apparatus



March 31, 1953 Filed July 12, 1948 R. J. KUTZLER FLIGHT CONTROL APPARATUS F .la

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R. J. KUTZLER FLIGHT CONTROL APPARATUS March 31, 1953 2 SHEETS-SHEET 2 Filed July 12, 1948 HMP To ELEVDN m ngvo/v AAA Patented Mar. 31, 1953 FLIGHT CONTROL APPARATUS Robert J. Kutzler, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 12, 1948, Serial No. 38,272

14 Claims. 1

This invention pertains to steering mechanisms for dirigible craft such as flight control apparatus for aircraft.

This invention, more specifically is concerned with an arrangement whereby the control surfaces which control the position of an aircraft about three axes may have the power means which operate them manually or automatically controlled.

This invention is an improvement in the control apparatus disclosed in the application of Robert J. Kutzler, Serial Number 14,787, filed March 13, 1948. The aforesaid application discloses control apparatus, for a type of aircraft known as the flying wing, wherein the aircraft may be automatically stabilized in heading and in a horizontal plane and in addition may have its heading altered by a manual controller operating through the apparatus.

It is an object .of this invention to provide alternative manual operable means operable in several directions for controlling the aircraft through the control apparatus.

It is a further object of this invention to provide selective positionable means for providing various associations of the alternative manually operable means and the automatic control apparatus of said prior application whereby various operations of the control surfaces are secured.

These and other objects of the invention will be evident from a consideration of the following description with reference to the accompanying drawing disclosing a preferred embodiment thereof.

Figures 1a and lb together illustrate a schematic arrangement of the component parts of the control apparatus forming the novel subject matter of this invention.

An aircraft of the flying wing type as dis closed in United States Patent 2,412,647 is controlled about its three axes while in flight by two sets of control surfaces. Control about the roll and pitch axes is provided by one set of control surfaces known as elevons which may be operated in opposite directions or in the same direction to provide the well known aileron and elevator function respectively. Control about the turn axis is provided by the other set of control surfaces called rudders.

Turn axis control As stated above, control of the flying wing about the turn axis is achieved by two so called rudders which are mounted in the outboard extremities of the wing one rudder being provided described, arrangements have been provided,

whereby only one rudder is in operated position at one time.

Considering the operating means for each rudder, the left rudder, not shown, is actuated by cables l0 extending from a cable drum II. The cable drum II is driven by a servomotor l2. The servomotor i2 is controlled by an amplifier l3. The amplifier servomotor arrangement may be similar to that disclosed in application 447,989,

filed June 22, 1942, or in Patent 2,425,733, issued August 19, 1947.

In the aforesaid application Number 447,989 a servomotor is reversibly controlled by an amplifier. The direction of rotation of the servomotor is controlled by two relays mounted in the amplifier. One or the other of the amplifier relays is operated depending upon the phase relationship between the voltage applied to a control circuit of the amplifier and a source of voltage for the amplifier. Each amplifier relay in the aforementioned application is in series with a limit switch which is operated by th servomotor after limited rotation thereof. After the servomotor has operated a predetermined extent, the limit switch is opened and prevents further operation of the servomotor.

In the arrangement of this invention, each rudder servomotor l2 and I2 is so adjusted with respect to its limit switches that in normal position the servomotor will have opened one limit switch. For example the motor I2 may, in ncrmal position, have opened its limit switch which is in series with the relay contacts in amplifier l 3 which are operated when a negative control signal is 'applied to amplifier l3. Thus even if a negative signal causes the amplifier to operate, the'operation of the relay in the amplifier will not effect rotation of servomotor l2. On the other hand a positive signal on amplifier l2 which effects operation of the other relay will cause servomotor l2 to rotate since the other limit switch in series with the other relay is closed. Similarly servomotor 12' in normal position has opened its limit switch which is in series with the relay in amplifier 13' which is operated when a positive signal is applied to amplifier l3. The

servornotor l2 will not be operated when a positive signal is applied to amplifier 13 but will operate when a negative signa1 is applied. With one limit switch opened in the normal position of the servomotor, only one relay in the amplifier is effective to initiate rotation of the servomotor from its normal position.

The amplifier I3 is connected by means of leads M'- and [5 to a source of voltage, not shown, which may be the inverter or other source of voltage for the aircraft. The control voltage for amplifier I3 is applied across inputileads. i6 and I1, and the voltage is derived from a circuit extending from lead ll, a rebalancing: impedance network 20, lead 35, lead 35', a vertical gyro rudder compensating impedance network 40, alead 55, a rate gyro signal network 50, a lead 75, a yaw signal network 80, a lead ['35, a resistor I38 of a rudder turn control trimmer potentiometer, a directional gyro pickup network I41, lead I50, to ground and to the grounded input lead It of amplifier l3-,

The impedancenetwork 25-inc1udes-a rebala-ncing potentiometer which has its resistor 21- connected by means of leads 2% and 25' to the opposite ends of a secondary winding 24 of. a transformer having aprimary winding 25. A wiper 21 of the rebalancing potentiometer is. operated by a follow up connection 28 from the servomotor 12-;

The servomoter of the aforementioned application also; drives a. wiper of a rebalancing potentiometer; and when. alimit switch. has. been opened, the wiper has: been. displaced to a maxi.- mum position. toward one end of. the potentiometen The: position of suclr follow up wiper on its potentiometer may serve as an: indication as to whether a limit switch. has been operated. To indicate that each of the rudder servor'notors in normal position opens one limitswitch in the arrangement of this invention a wiper on each rebalancing potentiometer as wiper 21 of network 20 assumes a position at one end of the potentiometer when the servomotoris in normal position. In this embodiment therefore, a signal voltage of one phase with respect to a source of voltage will cause one servomotor to operate and the other to remain unop'erated whereas a signal or different phase with respect to a source of voltage will cause the second servomotor to operate but' the first ser'vomotorwill remain unoperated. p I

Continuing, the network 20- also includesa centering potentiometer; which has. its resistor 30 connected by means of leads 22' and 23 to the opposite ends of the secondary winding 24. A wiper 3| of the centering potentiometer. may be manually adjusted. A rudder ratio potentiometer has one end of its resistor 33 connected to wiper 2 1 and has the other end connected to wiper 3!. The ratio potentiometer. has a manually adjustable wiper 34., In. normal position, the wiper 21. and. the wiper 3! are in thesame relative positionon their respective resistors at-which time. there is no difference of potential. between wipers. 2.7. and 31. Any change in the relative positions ofwipers. 2.1 and 31 will result in. a difference of. potential which will be. applied across the ends of resistor 33. The wiper 3.4 may be. adjusted. to select. any portion of. this potential. Wiper 34 is connected. to. lead H.

Since: network 20: and other networks tobe described. are energized by secondary windings which may have a common primary winding.

the primary winding is indicated in each instance by the reference character 25.

The rudder compensating network 40 includes a skid potentiometer having a resistor 31 connected by means of leads 42, 43 to the opposite ends of secondary winding 44 of a transformer having a primary winding 25. The skid potentiometer includes. a wiper 46 whichmay be actuated through an operativeconnecti'on 268 from a vertical flight gyro 353 to be describeddue to movement of the aircraft about its roll axis. A skid. trim. potentiometer has its resistor 49 connected' across the wiper 46 and a center tap 48 of. resistor 4 L A. wiper 58 of the skid trim potentiozneter: may be manually adjusted over the surface of resistor 49 and is connected through lead 36 and lead 35 to wiper 3| of network 20. one end of resistor 49 is also connected to a lead. 55.

The rate signal network 68 includes a centering potentiometer havinga resistor 61 whose opposite ends are connected by means of leads G2, 63 to the opposite ends oi secondary winding 54 of atransformer having a primary winding 25-. A wiper 65 or the potentiometer which may be manually adjusted over resistor 51 is connected to the opposite end. or lead 55. The network 6!} also includes a rate gyro potentiometer having a resistor 66 whose opposite ends are connected tothe: opposite: ends of secondary windin 64. A Wiper B1 of the potentiometer may be; actuated. through an operative connection 83 by a rate gyro Ill. The rate gyro 1.0 may be. of the conventional spring restrained. type used-.inturn indicators and applies its precessing movement: to. wiper B1 onmovement of the aircraft. about. its turn; axis. The-amount of move ment given wiper. 61 depends upon the rate at which the aircraft is turning. It may be seen that; the network. 60 isin the form of a Wheatstonebridge in: which an output voltage is derived across wipers B5 and 51 when they are relatively displaced; difierent amounts from the electrical centers of. their: respective resistors 61, 66-. The wiper 61 is connected to one end of lead 15.

The yaw signal. network 80." comprises a potentiometer having aresistor; 89 whose opposite ends are connected; by means; of; leads 8!, 82 to the opposite ends of a. secondary winding 83 of a transformer having a primary winding 25. The potentiometer has a wiper 8 which may be adjusted over the surface of. resistor 89. The network 30 includes a potentiometer having a resister 85 connected. to the opposite ends of secondary winding 83; by means of leads 8!, 82. A wiper 853 may be manually adjusted. over the surface of resistor 85. A voltages dividing potentiometer has a. resistor 81; which. has one end connected to wiper 8'4 and its opposite end connected towiper 8E. AwiperBB may be positioned over the. surface of resistor 81 and the wiper 88 and resistor 81. constitute; a yaw trim potentiometer or voltage divider to. select. any desired portion of the voltage between wipers 84, 86. Wiper M is connected to the opposite end of lead 75. The wiper 84' may be. actuated through an operative connection 90' from an alternating current motor 9!.

The motor 9! may be reversibly controlled by an amplifier 92.- Such amplifier motor combinations. are well known in the. art; and may be of the type shown in the United States patent to Whitman Nor 1,942,587 or Anschutz-Kaempfe No. 1 ,586,233, The direction of motor rotation depends on the phase relation between a control and a supply voltage.

The amplifier 92 is controlled in one instance through a circuit comprising a relay operated switch arm I00, out contact IOI, an impedance network I05, to ground, and to the grounded input of amplifier 92. The network I05 includes a yaw pickup potentiometer having a resistor I06 whose opposite ends are connected by means of leads I01, I08 to the opposite ends of a secondary winding I09 of a transformer having a primary winding 25. A wiper IIO may be positioned over the surface of resistor I06 by a vane Ill which responds to the relative wind and aligns itself therewith. The network I 05 also includes a vane centering potentiometer having a resistor III whose opposite ends are connected to the opposite ends of secondary winding I09 by means of leads I01, I09. A wiper H2 may be manually positioned over the surface of resistor I II. A voltage dividing resistor H4 has one end connected to wiper H and its opposite end connected to wiper H2 and to ground. A wiper H may be positioned along the surface of voltage dividing resistor H4. The resistor H4 and the wiper II5 constitute a vane trim potentiometer. The wiper H5 is connected to out contact IOI.

Normally the direction of heading of the aircraft is aligned with the direction of motion of the relative air and in such condition the wiper I I0 is at the electrical center of resistor I05. Any change between the heading of the aircraft and the direction of the relative air is an indication that the aircraft is in a yawed condition which will cause the vane H1 to be rotated thereby displacing wiper H0 along resistor I03. The wiper H2 may be manually adjusted so that in normal position no voltage will appear across wipers H0 and H2. Any voltage appearing across Wipers H0, H2 because the aircraft is in a yawed condition will be applied across the ends of resistor H4 and wiper H5 may 'be positioned along resistor H4 to select any desired portion phase of the source of voltage additionally supplied amplifier 92 and motor 9|, which may be the inverter previously mentioned.

When switch arm I00 engages its other contact, I02, the network I05 is disassociated from amplifier 92 but the amplifier 92 in this instance has its control elements connected to an additional source of voltage whereby the amplifier 92 may control the motor ill to recenter the wiper 84.

This additional source of voltage comprises an impedance network I which includes a yaw recentering potentiometer having a resistor I2I whose opposite ends are connected by means of leads I22, I23 to the opposite ends of a secondary winding I24 having a primary winding 25. A wiper I25 may be adjusted over the surface of resistor I2I by motor 9I through operating connection 90. Wiper I25 is connected to contact I02 by means of lead H9. The impedance network I20 also includes an aligning potentiometer having a resistor I21 whose opposite ends are connected by means of leads I22, I23 to the opposite ends of secondary winding I24. A Wiper I28 which may be manually adjusted over resistor I21 is connected to ground.

During the time that a yaw indicating signal voltage is being obtained, the switch arm I00 may be in engagement with contact IOI. Movement of vane H1 is transmitted to wiper H0 which is displaced from the electrical center of resistor I00. This displacement will result in a voltage drop existing between the ends of resistor H4 and a portion of this voltage is applied by wiper II5 through contact IOI and switch arm I00 to one input control lead of amplifier 92, the other input control lead of amplifier 92 being connected to ground as is also the lower end of resistor II 4. The voltage drop between Wiper II 5 and one end of resistor H4 will therefore be applied to the input control elements of amplifier 92 which thereupon operate and cause the motor 9I to position the wipers 84 and I25 through the operating connection 90. The displacement of the wiper I25 will result in a potential being developed across wipers I25 and I28. The switch arm I00 may now be brought into engagement with contact I02, whereby the wiper I25 through lead II 9 is connected to one control input of amplifier 92. The other control input to amplifier 92 being connected toground is also connected to the grounded wiper I28 of network I20. The potential between wipers I 25 and I28 being thus applied to the inputs of amplifier 92, the amplifier 92 causes the motor 9| to return the wipers 84 and I25 to their non-operated positions.

The yaw trim potentiometer of impedance network 80 has its wiper 88 connected to one end of lead I35. The opposite end of lead I is connected to a wiper I31 of a turn control trimmer potentiometer. This trimmer potentiometer has a voltage divider resistor I38 over whose surface the wiper I31 may be manually adjusted. One end of resistor I39 of the trimmer potentiometer is connected to a wiper I40 of a directional gyro rudder pickup potentiometer. This rudder pickup potentiometer constitutes a portion of impedance network MI and comprises a resistor I42 whose ends are connected by means of leads I43 and I44 to the corresponding ends of a secondary winding I45 of a transformer having a primary winding 25. The impedance network I4I includes a rudder pickup aligning potentiometer whose resistor I40 has its ends connected to the corresponding ends of secondary winding I 45. A manually positioned wiper I49 of the aligning potentiometer is connected by means of lead I50 to ground. The network MI is therefore in the form of a Wheatstone bridge in which the output is developed across wipers I40 and I49. In normal position, the wipers I40 and I49 are at the electrical centers of their respective resistors I42 and I48 at which time there is no potential difierence across the wipers.

The wiper I40 is operated. by an actuating connection I50 extending from a directional gyro I55. The directional gyro I may be of the conventional type such as that disclosed in the aforementioned application 447,989. In this arrangement the rotor of the directional gyro I55 tends to maintain its direction in space. Through the operative connection I59 the gyro rotor also tends to maintain the wiper I40 in a set position. The resistor I42 on the other hand is mounted on the aircraft and may partake of its movements; therefore, when the aircraft changes its heading by moving about its turn axis the resistor is displaced with respect to the wiper I40.

The resistor I30 of the rudder turn control trimmer potentiometer forms part of the conaesasee trol-circuit off the. rudder amplifiers I3, I37. Resistor I 38 constitutes:partofan additional circuit which: extends from its: other end, lead I59 to a wiper. IGI of a manually operated turn control rudder network I63.

' The turn control rudder network I53: has a resistor I62 whose opposite ends are connected through leads I64, 65 to the opposite ends of a secondary winding I67 of a transformer having a primary winding 25. The wiper I6I receives its adjustment through an operative connection I H from a manually operatedturn control knob I781 The resistor N52 has acenter tap Ifiilof considerable width so that it will require an extended displacement of wiper IEI before a difference of potential will exist between wiper IiiI and centerta'p 558. Center tap IEB-is connected by means of alead Il to a center tap I78 of a resistor I19 included in a formation stick rudder network I83 (Figure lb). The resistor I79 oi the network I83 has its opposite ends connected by means of leads I80, i8I to the opposite ends of a secondary winding I82 of a transformer having a primary winding I85. A wiper I8! of the formation stick rudder potentiometer may be positioned along the surface of resistor I19 and since the center tap I18 of the resistor is of considerable length an extended movement of the wiper I87 is required before a voltage will develop between wiper I81 and centertap I18. The wiper I8! is connected by means of a lead H38 and a lead I89 to a switch arm 353. When switch arm 45!! engages a contact sfiI it connects with the lead IQI which in turn is connected to a lead I92 to the opposite end of resistor I38 to complete the additional circuit associated therewith.

The right rudder, not shown, is operated by means of cables It extending from a cable drum II which is operated by a servomotor 2. The servomotor I2 is controlled by an amplifier I3. The amplifier servomotor combination for the right rudder is identical with that for the left rudder. V

The amplifier I3 is connected to a source of voltage which may be the inverter for the aircraft. and additionally has an input control signal applied across input leads I6, I7. The control input lead it is: connected to ground and the lead I?" from amplifier I3" is connected through an impedance network and a lead 35' to a portion of a circuit common to amplifiers 53, I3 comprising lead 36, network as, lead 55, network 68, lead 15, network 80, lead I35, resistor i353, network I41, lead 158 to ground.

The impedance network 20 includes a servomotor operated balance potentiometer having a resistor 2! whose ends are connected by means of leads 22' and 23' to the opposite ends of a secondary winding 24 having a primary winding 25. A wiper 21' of the servo balance potenticmeter is moved through a follow up connection 28 from servomotor I2. The impedance network 20' also includes a centering potentiometer which has a resistor 33' having ends connected through leads 22', 23 to the corresponding ends of secondary winding 24. The centering potentiometer has a manually adjustable wiper 3i which may be moved over the surface of resistor 30'. The impedance network 28 includes a ratio potentiometer which has its resistor 33 connected across the wipers 2'! and St. A manually adjustable wiper 34' of the ratio potentiometer may be adjusted over the surface of resistor 33. Lead I? from the amplifier connects with the wiper 34", and the wiper 31' is connected through a lead 35 to: lead; 36: and: thence: to. the: common portion of the control circuit for: amplifiers From what has been stated above it may be observedbriefiy that each of the rudder amplifier input circuits contains the following:

A source of signal responsive to the movement of the plane about the roll axis and as applied by the verticalflight gyro through network 40;.

A rate signal network controlled by a rate gyro Ii! which signal is developed in network to;

A yaw signal network which is controlled by the yaw sensing element I'I'i';

A directional gyro pickup network MI. which responds to changes in heading of the craft;

A manually operated turn control rudder potentiometer N35 for manually initiating operation or the rudder;

A formation stick rudder potentiometer I83 for initiating operation of the rudder by an additional manual means;

And to balance these signal voltages the input for the amplifier also includes a servo balance network 28 or 28' for bringing the circuit of the amplifier back to a balanced condition.

Ele'von control The aircraft is controlled about the roll and pitch axes by a single set of control surfaces called elevons whose structure is similar tothe conventional ailerons. One elevon is mounted in each wing near the outboard extremity thereof. At times these elevons are moved together inthe same direction at which time they effect a movement of the aircraft similar to that obtained by the conventional elevators. At other times the elevons are moved in opposite directions and provide a control effect similar to that provided by the conventional ailerons.

Referring to Figure lb, the left elevon, not shown, is actuated by a cable 2% extending froma cable drum 2M which is operated by a servomotor 202. The servomotor 202 is reversibly controlled by an amplifier 293. The amplifier servomotor combination may be the same as that disclosed in the aforementioned application No. 447,989, filed June 22, 1942, for operating a control surface. The amplifier 203 has power terminals 2'53, 235 connected to a source of voltage which may be the inverter for the aircraft. The control input signal for amplifier 293 is applied across connections 206, 207.

The right elevon, not shown, is operated by cables 20% extending from a cable drum 2M. The cable drum 29I' is driven by a servomotor 2832' which is reversibly controlled by an amplifier 2933'. The amplifier servomotor combination is similar to that used for operating the left elevon. The amplifier 253' has connections 294', 205' extending to the same source of voltage as conductors 20d and 235'. The control signal for the amplifier 203' is applied across leads 296', 201.

Since the amplifiers 283, 263' are to control their respective servomotors 292, 282 to effect the aileron and elevator action of the elevons. it is necessary to provide two types of controls for the amplifiers 283, 293'. The control of the amplifiers whereby the servomotors 262, 202' are operated to move the elevons in opposite directions to obtain the aileron function will be considered first.

The aileron control signal to the amplifier 203 which is applied across input leads 206, 20! is derived from a circuit extending from lead 206, an impedance network 2H], lead 224, a resistor 225;

tional gyro banking potentiometer. end of resistor 239 is connected by means of leads resistor 261 and awiper 261.

r from a vertical flight gyro.

a lead 221, an impedance network 236, a lead 248, a switch arm 6| 1, out contact 613, lead 252, an impedance network 266, lead 286, an impedance network 284, lead 316, an aileron turn control trimmer potentiometer 313, lead 314, a turn control aileron network 322, lead 326, a switch arm I 416, a contact 412, a contact 462, a switch arm 466, lead 331, a formation stick banking network 331, wiper 338 to ground and to amplifier ground lead 261.

Impedance network 216 comprises a servo balance potentiometer which has a resistor 21 1 connected across a secondary winding 214 by leads 212, 213, said secondary winding 214 having a primary winding 25. A wiper 215 of the servo balance potentiometer is adjusted over the sur face of resistor 211 by means of a follow-up connection 216 extending from servomotor 262. The impedance network 216 includes a centering potentiometer having a resistor 211 which is connected across secondary winding 214. A wiper 216 of the centering potentiometer may be manually adjusted over the surface of resistor 211. A voltage dividing resistor 226 has one end connected to wiper 215 and its other end connected to wiper 218. A tap 221 may be manually adjusted over the resistor 226. The resistor 226 and tap 221 constitute a ratio potentiometer whereby any desired portion of the voltage between wipers 215, 218 may be selected. The input lead 266 connects with wiper 221. Wiper 218 of network 216 is connected through lead 224 to one end of the resistor 225.

The impedance network 236 comprises a directional gyro banking potentiometer having a resistor 231 whose opposite ends are connected to the same end of a secondary winding 234 of a transformer having a primary winding 25. A broad center tap of resistor 231 is connected through lead 231 to the opposite end of secondary winding 234. A wiper 235 is adjusted over the surface of the banking potentiometer resistor 231 through an operative connection 236 from the directional gyro 155; The wiper 235 is connected by means of a lead 238 to one end of a resistor 239 which constitutes a portion of a second direc- The opposite 246, 231 to the center tap of resistor 231. A wiper 241 may be adjusted over the surface of resistor 239 through an operative connection 236 from :dir'ectional gyro 155.

245 is connected by means of lead 221 to the I opposite end of resistor 225. The end of resistor 244 connected to the center tap 243 is also connected by means of alead 248 to switch arm 61 1.

Impedance network 266. includes a vertical flight gyro roll axis potentiometer which has a The resistor 261 has one end connected through lead 263 to one end of a secondary winding 264 .of a transformer" having a primary winding 25; the oppositeend of resistor 261 is connected by means of lead 262 and -a variable resistor 265 to the opposite end of secondary winding 264; The wiper 261 is adjusted over resistor 261 by an operative connection 268 The wiper 261 is connected by means of lead 252 to an out contact 813which may be engaged by arm 61 1 when the arm.is in the: lower. position. Impedance net- ,coacts with switch arm 611.

ually adjusted over the surface of resistor 216.

The impedance network 266 is provided with an additional potentiometer whose resistor 212 has one of its ends connected directly to one end of secondary winding 264 and has its other end connected through variable resistance 265 to the opposite end of secondary winding 264. The additional potentiometer has a wiper 213 adjustable over the surface of resistor 212. This wiper 1213 is connected to the in contact 612 which A lead 286 extends from wiper 211 of network 266 to impedance network 284 (Figure 1a).

Impedance network 284 includes a potentiometer having a resistor 285 whose opposite ends are connected by means of leads 286 and 281 to the opposite ends of a secondary winding 296 of a transformer having a primary winding '25. The impedance network 284 also includes a resistor 293 which has its opposite ends connected to the corresponding ends of secondary winding 296 by means of leads 286, 281. A voltage dividing potentiometer has a resistor 294 having one of its ends connected to a center tap of resistor 293 and has its opposite end connected to lead 286 and thereby to wiper 291. A wiper 298 may be manually adjusted along the surface of resistor 294. Wiper 291 is actuated by an operative connection 295 extending from a motor 296..

The motor 296 is reversibly controlled by an amplifier 291. The amplifier 291 and motor 296 may be similar to amplifier 92 and motor 91 previously described. The control input voltage source for amplifier 291 comprises a circuit extending from input lead 366, switch arm 362, out contact 363, switch arm 366, out contact 361, lead 368, impedance network 141, lead 156 to ground, and to the grounded input terminal 361 of amplifier 291.

Wiper 298 of network 284 is connected by means of lead 316 to wiper 311 of the aileron turn control trimmer potentiometer 313 (Figure 1b). One end of a voltage dividing resistor 312 of the potentiometer 313 is connected to ground and the opposite end of resistor 312 is connected by means of lead 314 to wiper 316 of the turn control aileron potentiometer. The turn control aileron potentiometer includes a resistor 311 whose opposite ends are connected by means of leads 318, 319 to the opposite ends of a secondary winding 321 of a transformer having a primary winding 25. The wiper 316 which may be positioned over the surface of resistor 311 derives its movement through an operative connection 111 from the turn control knob 116. A

center tap of resistor 311 may be connected by .means of lead 3211, switch arm 416, contact 412,

contact 462, switch arm 466 to lead 331; network 331 to ground and to the grounded end of resistor 312.

2 IB extending from servom'otor 202*. .ped-ance network 210' includes a centering'p'otentio'meter which has a resistor '2I1' and wiper ace'ae re 11 tion of "servomotor 202 for the right elevon "is itself controlled by a circuit extending from input lead 206, impedance network 2-I0, lead 224', resistor 225, lead 221, impedance network 230,

lead 248, switch arm BI I, out contact 613, lead amplifier 203'.

Impedance network 2 I0 comprises a servo balance potentiometer which has a resistor 2II' whose ends are connected through leads 2 I2, 2 I 3 to the opposite ends of a secondary winding 2I4' of a transformer having'a primary winding 25. A wiper 2l5' is adjusted over the surface of resistor 2| I by means of a follow up-connection The im- 2I8'. The ends of resistor -2I'i are connected 'by leads 212 2I3' to the oppo'site'ends of "secondary winding '2I4'. The "wiper 2I8 may be manually adjusted over the surface of resistor 2I1'. A ratio or voltage dividing potentiometer has aresistor'220' which is connected across wipalong resistor 220. Tap 22! is connected to lead200. Lead 224' -is connecte'dto the junction of wiper 2I8 and resistor 220. The lead 224 extends to 'one end of resistor 225', and the opposite end of resistor 225' is'connected to lead 221. The additional impedance elements which form a portion of the control circuit for amplifier 203' for providingaileronaction have'been previously described in connection with the input circuit of amplifier 203.

Briefly it appears from what has been described above that the control circuits for the respective amplifiers 203, 203 for the elevons which circuits provide the aileron effect includes as follows: a network 230 which is controlled by the directional gyro upon deviations of the aircraftabout the vertical axis; an impedance network-260 controlled by the vertical flightgyro upon'movements of the craft about the roll axis; anetwork 284 for applying a permanent retrim o signal upon deviations about the turn axis; "a

manually controlled aileron potentiometer operated by the turn control knob I10 to provide banking of the plane when it is manually turned;

a formation stick banking network 331 whereby the plane may be banked when an additional manual control is operated; and a balancing network driven by the motor which positions the controlsurface whereby the input/circuit for the amplifier is balanced.

Elevator control of the elevons The control circuits previously described "for amplifiers 203, 203' whereby 'aileronaction is obtained include as a portion thereofthe'space ends of resistor 225' from the control'circuits efiecting aileron operation of V amplifiers '2 03 52 03.

' winding 315.

:gyro 363.

and amplifier 203' for obtaining elevator .ac tionof amplifiers 203, 203', a voltage drop across resistor 225 and resistor 225' is provided. Where operation of the amplifiers 203 and 203' iseiiected to produce elevator action the resistors 2-25, 22-5 serve as voltage dropping resistors.

The voltage drop across resistors 225, 225 is obtained from a circuit extending from the right end of resistor 225','1ead 350, impedance network 35!, lead 368, impedance network 310, lead 39.0,, out contact 619, switch arm-6H, lead .393,'t.o'the mid-point of "a resistor 394, through the left portion of resistor 394, lead 408, formation stick elevator potentiometer 400, lead 4 I 2, lead 413, re-

sistor 225, and to the left end of resistor 225'.

Thus thecombined voltages across networks .351

and 310 the left handportion of resistor 304=and network 400 areapplied to resistor 225 andl225' -in series.

The impedance network 35I comprises anelevon centering potentiometer which has a resistor 352 whose opposite'ends are'connected by means of leads 354, 355 to the opposite ends of a secondary Winding 356 of a transformer having a primary winding 25. A wiper 351 may be manually adjusted-over the surface of resistor 352.

Lead 350 extends from the right endof resistor 225' to the wiper 351. Impedance network 35I includes a pitch axisjpickuppotentiometer'having a resistor 359 whose'opposite ends are connected by means of leads 354'and 355 to the-opposite ends of secondary winding 355. A wiper 360 of the pickup potentiometermay be adjusted along resistor 359 and receives such adjustment through amechanical operating connection 362 from a vertical fiight-gyro363. The vertical flight gyro 363 may be of any conventional type, one suitable type being that disclosed in the aforesaid application 441,989. Relativemovement be tween the gyro 363 and the aircraft due to the movement of the aircraft about the pitch axis is transmitted through the operating connection 362 to the wiper 300. Ari-additional potentiomsecondary winding 356.

The impedance network 310 comprises anup elevon vertical flight gyro roll axis operated-potentiometer having a 'resistor'31 land a wiper 316. One end ofvresistor 31I .is connected by means of lead 314to one end of a secondary winding 315 of a transformer-having a primary winding '25. The opposite end of resistor 31I is connected by means .of lead 313 .to the same'end of secondary The wiper :316 may be adjusted along the surface of resistor 31I by a mechanical connection208 extending from'thevertical fiight Relative movements between the aircraft and thevertical flight; gyro 303 due to the movements of the aircraft about the roll axis are transmitted through the connection 2 68 to wiper 310. Impedancenetwork 31-0 includes an up elevator trimmer potentiometer ("having a resistor 38I whose opposite :ends are connected to the opposite'ends of secondarywinding315. A wiper 380 may :be manually adjustediover resistor 38 I Aconnection extends from wiper 380 to aacenter tap 311 of .resistor31I. 'A lead 308iextends from wiper 360 ofimpedancenetworkfil tothe wiper 380 of impedance network 310.

The formation stick elevator potentiometer ary winding 402 of Y a transformer having va:.-pri- 'mary winding-IM. -A'wiper -wll may be adjusted over the surface of resistor 40 I. The resistor 40l has a broad center tap 403 which connects by means of lead 408 to resistor 394 and through a portion of resistor 394, lead 393, switch arm 6H, contact Hi9, lead 390, to wiper 316 of network 370. Wiper 489 of potentiometer 40B is connected through leads M2, M3, to the left end of resistor 225.

The control circuit for amplifier 203 to obtain elevator action includes two active elements which are the impedance network 210 and the voltage dropping resistor 225. Likewise the control circuit of amplifier 203' for elevator action includes the active resistor 225' and network 2l0. Other impedance networks common in the control circuits merely perform a passive function in the input circuit of amplifiers 203, 203' for obtaining elevator action. The inactive portions of the circuits comprise lead 221, impedance network 23%, lead 248, switch arm 61 i, cut contact 6l3, lead 252, impedance network 250, lead 280, impedance network 284, lead 3), trimmer potentiometer 313. to ground.

Function selector A function selector is designated generally at 449. The function selector comprises seven switch sections. Each switch section includes a contact arm and four coacting contacts for the arm. The switch arms of the sections are operatively connected by means not shown for ganged operation. As indicated in the top section, the switch arms may be placed in any of four positions. The position assumed by the function selector determines the interrelationship of the automatic and manual controls for controlling the control surface operating mechanism.

The top or first switch section is associated with elevator control of the elevons and comprises a rotatable switch arm 44!, three inoperative contacts which are in the first, second, and third position of the function selector and one operative contact 443 which is in the fourth position of the function selector.

A second switch section is associated with control of the rudders and comprises a rotatable switch arm 45!}, two inoperative contacts in the first and second function selector positions and two operative contacts 45! and 452 of the third and fourth positions respectively of the function selector.

The third switch section is associated with aileron operation of the elevons and comprises a rotatable switch arm 460, one inoperative contact in the first position of the function selector, and three operative contacts 46!, 452, and 463 in the second, third, and fourth positions respectively of the function selector.

The fourth switch section is also associated with aileron operation of the elevons and comprises a rotatable switch arm 41!], an inoperative first function selector position contact, an operative second position contact 41!, an operative third position contact 412 and an operative fourth position contact 413. A resistor 33!! is connected across arm 46!] of the third switch section and arm 410 of the fourth switch section.

The fifth switch section is associated with a servo boost relay 600 and comprises a rotatable switch arm 480, an operative first function selector position contact 48!, and inoperative sec- .ond, third and fourth position contacts. 1 v The sixth switch section is associated with primary winding I84 of the formation stick netw an om s a t table w i herm 49.9

14 an operative first function selector position contact 492, an inoperative second position contact, an operative third position contact 493, and an operative fourth position contact 494.

The seventh switch section is associated with an erection cutout for the vertical gyro and comprises a rotatable switch arm 500, an inoperative first function selector position contact, an inoperative second position contact, an operative third position contact 50!, and an inoperative fourth position contact.

Formation stick A formation stick is generally indicated at 5H3. This formation stick comprises a manually operable member 5 which has an enlarged lower section H2. The section 5|2 has laterally extending trunnions 5| 3 andv 5| 4 whereby it is mounted in a bifurcated member 5I5. The bifurcated member 5! 5 is fixed to a shaft 5H5 which in turn is pivotally supported by two spaced brackets one of which is shown at 511. The mounting of the formation stick is such that when movement is applied to the control member 5H in a fore and aft direction of the aircraft or perpendicular to the plane at the drawing the trunnions 5l3, 5l4 pivot in the bifurcated member 5B5. When the manual member 5 is given a lateral movement in the aircraft or in the plane of the drawing the bifurcated member 5| 5 pivots with shaft BIS rotatably mounted in the brackets 5|! which are in the longitudinal plane of the aircraft. It is therefore seen that the movement of the member 5| l and trunnions 5I3 and 5M in the bifurcated member 515 is similar to the movement of the conventional stick of the airplane in elevator control and that movement of the members 5H, 5l5 with shaft 5I6 about the axis in the longitudinally spaced brackets is similar to the movement of the ordinary stick of the aircraft in applying movements of the ailerons. Movement of the member 5 with its trunnions 5l3 and 514 is communicated through an operative connection 518 to the wiper 409 of the formation stick elevator potentiometer network 4530. Movement of the member 5I5 and shaft 5l6 is communicated through an operative connection 520 to the wiper I81 of the formation stick rudder potentiometer network I83 and to the wiper 33B of the formation stick banking potentiometer network 331.

A switch arm 530 mounted on the member 5H5 of the formation stick coacts with two spaced contacts 53I and 532. The spaced contacts 53! and 532 are connected together.

Servo boost relay respectively with contacts 604, 605; M2, M3; H8,

A directional arm lock which has a coil 608,

'Figure 1a, and which may be of the type describedi-n application 447,989 previously referred .to coacts with the directional gyro. The directional arm lock serves during manually initiated turns to prevent the transmission of movement from the directional gyro to, other elements vor signal voltages.

T5 in the night control system controlled ethereby, including wipers 140, 235, :and 24!.

The manually operated turn control .knob I10 operates through :a mechanical connection l'H an eccentric 640. Theeccentric 64B coacts with three contact bearing spring :arms 64], 1642 and 43. Upper armfi-M has :a =lower contact. .Mid- -dle:arm 642 has an upper and a lower contact. Lower contact arm 643 :has an upper :contaet. Rotation "of eccentric 640 in eitherdirecti'on depresses arm 64! and causes the :lower .contact of arm GM to engage the upper contact of arm 642 and also depresses arm '642 and thereby causes the lower contact of arm 642 to engage the upper contact of arm 64 3. The upper arm 641 is "connected to the directional arm lock'coil 8'08 and through a lead 648 is also connected to a centering cutout relay coil 659 whose opposite end is :connectedto ground. The relay coil 639 operates its relay arm 31%)! which coacts with two spaced contacts "-303, 303. The middle arm 542 is connected to a battery 4 whose opposite terminal is grounded. The lower arm 643 is connected to one end of the erection cutout coil '55! which :is associated with "the erection means for the vertical flight gyro to rendersuch erection means inoperative, as disclosed in :the aforementioned application 547,989.

A centering control relay for impedance networks 80 and 284 comprises operating coil 1-83; switch garms I00, 3.06; in contacts H52, 365; "and out contacts till, {301. Arm Hi coacts with spaced contacts l 0l and 102. .SwitcharmBOt coacts with spaced contacts 305 and 301. coil )3 has "one end connected to ground and has its other end connected by ,means of a lead 65! to a battery 652. The opposite end of the battery 652 is connected to va contact of a single-pole single-throw switch whose arm "65A is connected to ground.

Adirectional gyro panel switchincludes upper arm Eli-land alowerarm 614. The .arm 6l3'has has a cam element '61 which coacts witha rack 612. Rack F12 mayhedriven iby pinion ,511 on a connection 61.0 from ,the directional gyro 455.

Rudder amplifier l3, ,as stated, .is controlled by a signal voltage applied across terminals 15 and I l. The input control :circuit previously :recited for amplifier l3 includes impedance networks which themselves constitute sources of control If iwipers ,2! ,and ill of ,impedance network are notat thesame relative position on their respective resistors 21 and to,

a diiierence of potential will exist between the wipers 2'! and 3!. This voltage is applied to the ends of resistor 33. A portion of this voltage drop will therefore appear between wiper 34 and the lower .end of resistor 33.

Similarly, iftwiper #6 is :not at the center'atap -48 of network 10, a "potentialwill exist between wiper 46 and a centertap 48 which .is applied to .the ends of resistor 49. Aportion of this voltage will appear between wiper- 50 '-and the lower end of resistor 49. This voltage between wiper 50 and the -lower-end-of resistor =49 'is in series with the potential between wiper 3'4-and the lower end of resistor "33.

previously mentioned voltages.

if wiper M and wiper 8'6 of network have a relative displacement, a voltage difference will exist between wipers 8d and which will be applied across resistor'81 A portionrof this voltage will appear between theupper end of resistor 81 and wiper 88 which is in-series with theprevious'ly mentioned voltages.

If wiper i6! of the turn control rudder potentiometer is not at center tap I58 of=resistor 1 62 a potential difierence will exist between wiper 4 61 andcenter tap +68. This potential is applied on one *hand from wiper flii lead I68 to one :end-of resistor 138 and on the other hand from center tap 1.63, lead H5, formation stick rudder potentiometer network 1-83, center rtap I18 thereof, wiper :itllead i aresistor A58, lead I92 to the other end :of resistor .138. The .potentlaldlfierence :acrossthe ends of resistor L38 may be obtainedeither from the relative displacement :of wiper 16! from center tap 1'52 ofrthe turn-control rudder network A63 or .by the displacement of the wiper i82 irorncentertap 11801 the formation stick rudder potentiometer. A portion of the voltage drop across the ends of resistor 138 will exist between wiper 1'3! and the left end of resistor 138 which portion is in series with the previously described voltages.

If wiper Hill of the directional gyrorudderpickup potentiometer has a relativedisplacement with respect to wiper M9 on the centering potentiometer, this voltage so derived will be applied in serieswith the voltage-derivedirom-the turn control trimmer potentiometer resistor I38.

The control voltagefor rudder amplifier 13' is obtained from ,a circuit analogous to that controlling amplifier 1,3 in that the voltage between wiper E i and the lower ,end of resistorl33' is in series with the voltageexisting between wiper 50 and the lowerend of resistor d9, between wiper-85 and wiper 87!, between the upper endof resistor 83 and the wiper ,88, betweenwlper 1.37 and the left end ofresistor ,l38, and between Wipers I40 .and149.

Initially, the input circuit is balancedand is inefiective to causetheoperation oframplifler [3. In this ineffective condition of the control circuit, the wipersr2l ands i are at the same relative posi- ;tions on their resistors and have no potential be- ,tween them, the wiper 46 is at the center tap 48 of the roll axis potentiometer ,40 and nopotential is applied across resistor 49, the wipers B5 and 61. are at the electrical centers of their respective resistors 6 l, 66 with no potential between them, the wiperst l .andtfi are at theelectrical centers of their'respective resistors and no potentialis appliedacrossresistorfll, the wiper J61 ofthe turn icontrol ruddernetwork-l 63.is at its center tap I68 and the formation stick rudder potentiometer wiper J 81 is atcentertap l l8 thereforeno potential isappliedacrossresistor L38 ,andno potentialisbetween wiper l3? and the .left end of re.- ,sistor J38, wiper tilt and wiper 149 are at the electrical centers of their respective resistors 142,158. In assimilarmanne f theamplifier i3 ,is'balanced and is inoperative initially at which time wipers 2i and 3I' are,at,.t he same relative Function selector position .No. 12

"For automatic stabilized flight and manual turn control,-the function selector "44 0 is considered to have;been operated so-that the-respective switch" arms of the seven switch sections engage their respective number 2 contacts as indicated in the first section at which position the apparatus operates as that in the aforementioned application 14,787. In other words, the function selector has been actuated from the present number 1 position as shown to the number 2 position. In this position, the formation stick 510 and its potentiometers are ineffective to control the control surfaces,

The secondary winding [82 of the formation stick rudder network, the secondary winding 335 of the formation stick bank network 337 and the secondary Winding 502 of the formation stick elevator network 465 have their primary windings I84 connected at one side directly to the source of voltage. The other end of the primaries 184 are connected through lead 498 to the contacts 492, 493 and 59d of the sixth switch section. These contacts are in the first, third, and fourth positions of the function selector. The other side of the source is connected by means of lead 595 to switch arm '35!) of the sixth switch section. Since arm 598 is now engaged with the inoperative function selector second position contact the primaries for the formation stick potentiometers are open.

Referring to the fifth section of the function selector, when the function selector Mill is in the second position, the relay coil 50! of the servo boost relay 553 which has one end connected to ground and which has its other end connected through lead 4182 to wiper 485 of the fifth switch section has its circuit open since wiper 485 engages the inoperative number 2 contact in the said section. The switch arms 5B3, 61 I, fill and 635 of the servo boost relay are therefore in the lower position or opposite from that shown in the figure.

In the seventh switch section of the function selector, a circuit for energizing the erection output cutout coil is open since wiper arm 550 is now engaged with the inoperative number 2 contact.

The turn control aileron network 322 has its center tap connected through lead 325, to wiper 410 in the fourth switch section and through 0perative contact Hi to ground. The wiper SIB of the turn control aileron potentiometer is connected to one end of the resistor 3I2 of the turn control trimmer potentiometer 3l3. The resistor (N2 of this trimmer potentiometer is connected to ground; therefore, movement of wiper 3 i 6 with respect to center tap 325 will cause a voltage drop to appear across the resistor 3l2 of the turn control trimmer potentiometer.

The resistor wt of the turn control'rudder trim potentiometer which has its energizing source supplied either by the turn control rudder potentiometer or the formation stick rudder potentiometer now has a circuit extending from the right end of resistor 138 through the turn control rudder network I52, lead I15, center tap I18 of the formation stick rudder potentiometer, wiper I87, lead [88, resistor 458, lead I92, to the left end of resistor 53B. The-engagement of wiper Q55 of the second switch section with the inoperative second function selector position contact prevents bypassing resistor 458 in the circuit energizing resistor [38.

Since the primary winding i8 3 which energizes the secondary winding 402 of the forma-' tion stick elevator potentiometer 400 has its circuit open at this time, the elevator potentiometer 43G merely serves as a conductor in the impedance network which energizes the resistors 225, 225' of the elevon networks. This energizing circuit extends from the left end of resistor 225, lead M3, wiper 309, center tap 453, the left portion of resistor 3%, lead 393, switch arm 5H, out contact 6H9, lead 390, impedance network 310, lead 358, impedance network 35!, lead 350, to the right end of resistor 225', through resistor 225 to the right end of resistor 225.

The manner in which impedance networks 35! and 310 energize the resistors 225 and 225' through the above described circuit may be considered. If wiper 351 and wiper 365 of network 351 are at the electrical centers of their respective resistors 359, 352 no voltage across wipers 35? and 565 exists. However, when these wipers 357 and 350 are displaced difierent amounts from their electrical centers a difference of potential will exist between the wipers and this difference of potential is applied through the aforesaid circuit to the resistors 225 and 225'. In a similar manner, wiper 316 of the roll axis up elevator impedance network 310 is at center tap 31? at which time the network 310 does not supply any voltage to the circuit for energizing resistors 225 and 225. If wiper 316 be displaced from center tap 377, a difference of potential between the wiper 315 and center tap 371 will exist and this is applied to the aforesaid circuit for energizing resistors 225 and 225.

The voltage drop across elevator action control resistors 225 and 225 resulting from the voltage derived from either network 35i or network 370 causes the amplifier 253 and amplifier 253' to effect operation of their servomotors *252 and 282' to provide an elevator action to the elevons. Through the discussion which follows, impedance network 351 is considered to be the only network which provides a source of voltage in the elevator circuit for causing a voltage drop across resistors 225 and 225'. Roll axis impedance network 375 is assumed to be in a balanced condition with wiper 315 at center tap 3'. The impedance networks 215 and 2m' are assumed to be in balanced condition with wipers 2 I5, 218 of network 2! at the electrical centers of their resistors 2 II and 2H and wiper H5 at the electrical center of resistor 2| l and wiper H8 at the electrical center of resistor 2H.

Assume in any half cycle that the right end of secondary winding 356 of network 35f and of other networks is positive with respect to the left end and that the voltage of the secondary .windings have the proper phase relation with respect to the supply to the amplifiers and motors and that wiper 350 has been moved to the right of the electrical center of 359 by the vertical gyro 353. At this time, wiper 355 will be positive with respect to wiper 357 since it is nearer the positive end of secondary winding 355. The wiper 351 i connected through lead 35s to the right end of resistor 225'. The wiper 360 is connected through the previously described circuit to the left end of resistor 225. The lead 221 which connects to the junction of resistors 225 and 225' is connected also as stated to ground. The connection from the junction of resistors 225 and 225' to ground does not modify the voltage drop across resistors 225 and 225. It merely serves as a ground connection. The left end of resistor 225 is at a higher potential than the right end, and it is connected through impedance network 2m to input lead 256 of amplifier 203. The lead 256 is therefore positive with respect to ground. The right end of resistor 225' is at a lower potential than its left end, and the right end is connected through network 2|0' to input lead 203' of amplifier 203'. At this time, therefore, the input lead 266 of amplifier 203' is negative with respect to ground. The amplifier 203 having a positive signal on input lead 206 operates oppositely from amplifier 203 which has a negative signal on input lead 206.

In the amplifier servomotor combination of the aforesaid application 447,989, each amplifier controls two relays or a pair of relays. For a positive signal on the amplifier, one relay may be operated which may control a circuit through a clutch operating solenoid whereby right rotation of a servomotor may be obtained. On the other hand a negative signal on the amplifier may cause the other relay to operate which closes a circuit for a clutch actuating solenoid which effects left rotation of the servomotor. If one servomotor is modified so that its clutch actuating solenoid which effects right rotation of the servomotor is now placed under the control of the amplifier relay operated by a negative signal on its amplifier whereas the other servomotor has its clutch which efiects right rotation of the servomotor under the relay controlled by a positive signal on the other amplifier. It is evident that a positive signal on the unmodified servomotor causes right rotation since its relay actuates the switch controlling the circuit through the right rotation clutch solenoid and that on the other hand a negative signal on the amplifier controlling the modified servomotor will energize the relay which has now been associated with the circuit for controlling the right rotation servomotor clutch. Therefore, in the present arrangement a positive signal on amplifier 203 and a negative signal on amplifier 203 causes both servomotors to rotate in the right or in the same direction to raise the elevons. Similarly, a negative signal on amplifier 283 and a positive signal on amplifier 203 causes the servomotors to rotate in the same direction to lower the elevons.

The operation of amplifier 203 due to a voltage drop across resistor 225 causes it to effect rotation of servomotor 202. The servomotor 202 through its follow up connection 2"; adjusts wiper 2|5 with respect to its normal position on resistor 2| and sets up a voltage between wiper 2 l5 and wiper 2 I8 which is applied across resistor 220. Movement of wiper 2|5 by the servomotor 202 continues until the voltage between tap 22| and the lower end of resistor 22-0 is equal and opposite to the voltage between the left end of resistor 225 and the right end of the resistor which is connectedto ground. In a similar manner the voltage drop across resistor 225' causes the amplifier 203' to effect rotation of servomotor 202'. The servomotor 202 through its follow up connection 2|6' moves rebelancing wiper 2|5' to derive a voltage between wiper 2|5 and wiper 2|8 which is applied across resistor 220', and wiper 2 5' is moved until the voltage across wiper 22| and the lower end of resistor 220' is equal to and opposed to that across resistor 225'. Thus up elevator movement has been applied to the elevons.

It has been stated that a positive signal on amplifier 203 and a negative signal on amplifier 203' causes the respective amplifiers to eifect rotation of their servomotors 202, 202' in the same direction to raise the elevons. It is apparent that the same signal on each amplifier for example a positive signal on amplifier 203 and a positive signal on amplifier 203" causes them to effect control of theirservomotors 202 and 202' so that the servomotors rotate in opposite directions with the left elevon raised and the right elevon lowered. Similarly, a like negative signal on both amplifiers 203, 203 causes them to effect rotation of their servomotors 202 and 202' to rotate in opposite directions to lower the left elevon and to raise the right elevon. This'opposite direction of rotation of the servomotors 202, 202 with a like negative signal on each amplifier 203, 203 is the reverse from that obtained 2% a like positive signal on each amplifier 203,

If the junction between elevator action control resistors 225 and 225 which has lead 221 connected thereto has its potentials raised above that of ground and if impedance networks 2"), 2 0 are in balanced condition, it is apparent that the input leads 206 and 206' of amplifiers 203, 203' have their potentials raised and are also positive with respect to ground. In such a case the like positive signal on both amplifiers will cause the servomotors 202, 202' to rotate in opposite directions. The junction between resistors 225 and 225 as stated is connected by means of lead 221, directional gyro aileron impedance network 230, lead 248, switch arm 6| I, contact 6|3, lead 252, vertical gyro aileron network 260, lead 280, aileron impedance network 204, lead 310, and through the turn control aileron trimmer potentiometer 3 3 to ground.

We may assume that impedance networks 230, 260, and 234 are in balanced condition.

An aileron control voltage may be obtained from the turn control aileron network 322 by displacing its wiper 3|6 with respect to its center tap on resistor 3". Suppose in a half cycle that the right end of secondary winding 32| of the turn control aileron potentiometer is positive with respect to its left end. If wiper 3|6 now be moved to the right from the center tap'of resistor 3|| it will be positive with respect to the center tap. The wiper 3|6 is connected to the right end of resistor 312 of the aileron turn control trimmer potentiometer 3|3. The center tap of resistor 3|! is connected through lead 320, wiper 410 of the fourth section in the function selector, contact 4' to ground and to the grounded left end of resistor 3 l2. The wiper 3 of the aileron turn control trimmer potentiometer is therefore positive with respect to ground. The positive voltage on wiper-3|| is transmitted through lead 3"), impedance network 284, lead 200, impedance network 260, lead 252, out contact 6|3, switch arm 61 I, lead 248, network 230, lead 221, to the junction of resistors 225 and 225'. This positive potential is applied through the impedance network 2|0 to amplifier 203 and through the impedance network 210 to amplifier 203. Since a positive signal is applied to both amplifiers 203, 203', they will effect operation of their servomotors 202, 202' as to cause them to rotate in opposite directions.

Similarly if wiper 3|6 b moved to the left of the center tap of resistor 3H and considering again that the right end of secondary winding 320 is positive with respect to the left end, the right end of resistor 3|2 will be negative with respect to the left end. The potential of wiper 3 therefore will be negative with respect to ground. This negative potential of wiper 3 is transmitted to the amplifiers 203, 203 whereby the servomotors 202, 202' are again caused to operate in opposite directions due to alike negative signal on both amplifiers. The negative signal causes the motors 202, 202' to rotate in reverse directions from the rotations caused by a positive signal on both amplifiers.

A positive signal applied to the junction of the resistors 225, 225' effects opposite direction of rotation of motors 202, 202. The servomotor 202 positions its rebelancing wiper 2I5 to the left through the follow up 2I5 and thereby derives a voltage between the wipers 2I5 and 2J8 which voltage is applied across resistor 220. Wiper 2I5 is moved until the voltage between tap HI and the lower end of resistor 22!) is equal and opposite to that existing between the junction of resistors 225, 225' and ground. The input circuit of amplifier 203 is therefore in balanced condition and the amplifier ceases to operate. Similarly, servomotor 202 positions its wiper M to the left through follow up ZIG until the voltage between tap HI and the lower end of resistor 220 is equal and opposite to the voltage between the junction of resistors 225, 225' and ground. It is now apparent how aileron operation of the elevon through the aileron control networks of amplifiers 293, 203 is obtained.

The rudder amplifiers I3, I3 are controlled by circuits which constitute voltage sources. These sources may be varied similarly in a manner to that provided in the control network for the amplifiers 283, 203'. The operation of the amplifiers I3, I3 may be initiated by varying the potential of the junction of leads 35, 35 with respect to ground.

With the rudder signal circuits balanced as stated previously, assume in a half cycle that the right end of secondary winding I45 is positive with respect to the left end. If wiper Hit of the directional gyro rudder impedance network I4I now be moved to the right of the center position on resistor I42 the wiper I48 will be positive with respect to wiper I49 which is connected to ground. The positive potential of wiper Mil is transmitted through turn control trimmer potentiometer resistor I38, lead i155, impedance network 89, lead 15, impedance network 68, lead 55, impedance network ll], lead 36, to the junction of leads 35, 35. The amplifiers I3, I3 will now have a positive signal applied thereto with respect to their ground connections I6, I6.

-It was stated earlier that each servomotor I2, I2 had operated one of its limit switches to open position when such servomotors had driven their follow up wipers to normal position. The servomotor I2 actuates the left rudder and the right servomotor I2 actuates the right rudder. The servomotor 12' cannot move to the right at this time when a positive signal is applied to the amplifiers since its limit switch is open; although, its amplifier I3 in operating a relay partially closes a circuit through a clutch operating solenoid which circuit includes the opened limit switch. The right servomotor I2 will therefore not operate to open its rudder. The left servomotor I2, however, will, upon operation of its clutch from a solenoid controlled by an amplifier relay, rotate to move its rudder toward the open position. At the same time, the motor I2 through its follow up 28 positions the rebalancing wiper 21 along resistor 21 to set up a Voltage between wiper 2'1 and wiper 3I. This voltage is applied across resistor 33. The movement of wiper 21 continues until the voltage between wiper 34 and the lower end of resistor 33 is equal and opposite to that between the junction of leads 35, 35? and ground. Atthis time the control circuit for mplifier I3 is balanced, and the amplifier no longer operates.

In a similar manner with wipers 21, 27' in normal position, if wiper I40 were moved to the left of its normal position, and if the right end of secondary winding I45 be again considered positive with respect to the left end, the wiper I40 would have a negative potential with respect to ground. This negative potential on wiper I40 is applied to the junction of leads 35, 35' through the previously described circuit. With impedance networks 29, 29' in balanced condition a negative potential at the junction of leads 35, 35' is also applied to input i! of amplifier I3 and input ll of amplifier I3. The negative signal on amplifier I3 causes the amplifier 3 to effect movement of the servomotor I2 which moves wiper 21 to the right from its leftward position. This servomotor I2 at the same time opens the right, rudder to increase the drag on the right wing. The wiper 27 is moved by the servomotor I2 to set up a voltage between wiper 21' and wiper SI. This voltage is applied across resistor 33'. The movement of wiper 2'! continues until the voltage between wiper 34 and the lower end of resistor 33' is equal and opposite to that between the junction of leads 35, 35 and ground. When such equal and opposite voltage is set up, the control circuit to amplifier I3"is balanced and the amplifier no longer operates. The servomotor I2 also ceases to rotate.

The servomotor I2 in its normal position where wiper 27 is to the extreme right on resistor 2I has one of its limit switches in open position. This limit switch is in a circuit also controlled by a relay in the amplifier I3. Since the circuit is open at this limit switch the servomotor I2 cannot rotate to apply left rudder even if the relay is operated in response to a negative signal on amplifier I3. Thus it may be seen how the rudder is operated when signals are applied to amplifiers I3, I3.

Having described the manner in which a control voltage may be derived in the input circuits for the amplifiers I3, I3, 2B3, 283', the operation of the system for automatic stabilization or number2 function selector positioned, may be continued.

With the function selector 440 in the number 2 position for conventional control, the aircraft is automatically stabilized in flight. At the time the automatic stabilization is initiated, the various impedance networks are considered individually balanced. The aircraft is assumed to be in level flight position and to be flying on its desired heading. The manually operable rccentering switch 55 i will have been operated previously to cause the relay H13 to operate recentering control switch arms I98 and 386. If wipers I25 of network I20 and 84 of network had been displaced from their normal position a signal between wiper I25 and grounded wiper I 28 would exist. Wiper I25 is connecetde through lead H9, in contact I62, switch arm Ilia to one terminal of amplifier 92. The other terminal of the amplifier is grounded and is therefore connected to wiper I28. Any voltage between wiper I25 and I28 would now cause the motor Ell to be operated by amplifier 92. The motor 9I through the operative connection 9Q will return wipers I25 and 84 to th normal position on their resistors I2I and 89 respectively.

Similarly, if wiper 29I of network 284 had been displaced from the electrical center of resistor 285, a potential between wiper 29! and the center acsaeis tap of 'resistor .293'wouldexist. Wiper 2.91 is :now connected through lead 656, in contact 3.35, switch arm .3313, out contact 333, switch arm 3B2, lead 303 to one input terminal of amplifier 291. The other input of amplifier 23'! is connected to ground through lead 391. The center tap of resistor 293 is connected through resistor 294, wiper 238, lead 319, wiper 31f, resistor 312 of potentiometer 313, and to ground. At this time with the turn control aileron potentiometer in balanced position no voltage is applied across the resistor 312; therefore, the potential of center tap 298 is the same as that of ground. The voltage between wiper 29! and ground being applied to the amplifier 291, the amplifier 29'! causes the motor 396 to move the wiper 291 through the operative .connection 295 to normal position on the electrical center of resistor 285.

Assume now that switch 654 is opened and that the aircraft is headed in the desired direction, but that it is moving in a direction other than that in which it is headed. The aircraft at this time is therefore flying in a yawed position oryawed attitude. With the aircraft flying in a yawed position, the vane i 1'! pivots to align itself in the direction in which the aircraft is moving and moves the wiper 110 from the electrical centerof resistor 136. If the craft be headed to the left of its direction of movement .or yawed to the left, the vane 1 1! through motor 31 positions wiper 84 of network 81! to the left thereby applying a negative signal on amplifiers 13, '13. Amplifier 13' .eifects the positioning of the right rudder to remove the yaw. Any change in heading incurred whil yaw is being removed results in rudder control signals being derived from the directional gyro network 141 and the rate gyro network 60 which oppose the signal from yaw network 83. However, since wiper 34 is moved as long as the aircraft is in yaw so that its posi tion depends on time, it is evident that the signal from the yaw network will prevail and force the aircraft to fly without yaw.

Any change in heading, as stated, while correcting for yaw results in the directional gyro 155 through operating means 235% operating the wipers 235 and 241 of the network 230 and wiper 231 of network 284 whereby the aircraft is caused to bank. The effect of the banked position also causes the aircraft to turn to its desired heading. Thus any yawed condition is corrected and the aircraft is maintained on its desired heading. It is evident that the degree of the bank is controlled by the directional gyro and vertical gyro signals with the latter also applying u e'levator and modifying the rudder operation. In a similar manner the attitude of the aircraft may be corrected if the craft be yawed to the right.

The aircraft is stabilized about the roll axis by the vertical gyro 333. Should the aircraft tilt to the left about the roll axis, wiper 267 is moved to the left thereby applying a negative signal to the elevon aileron function network causing the left elevon to be lowered and the right elevon to be raised. At the same time wiper 43 of network 43 is moved to the left to apply a negative signal in the signal circuits of amplifiers 13, 13' which results in the operation of the right rudder to check any tendency of the craft to deviate from its desired heading. Under the applied elevon movement the craft returns to normal position. The vertical gyro 363 also moves wiper 316 of network3'11l to apply a positive signal to amplifier 233 and a negative signal to amplifier 233' whereby the elevons are 7 24 moved einan upward direction to prevent loss of altitude.

If the craft tilts to the :right, the right elevon is lowered and the left aileron :is raised in response :to the signal from network 263; the left rudder is operated in response to a signal from network 40; and the left and right elevons are moved upwardly in response to a signal-from network 3'11].

The aircraft 'is-stabilized about the turn axis bytheidirectional gyro 155. For 'a'transient disturbance which turns the craft to the right from its desired "heading, the directional gyro moves wiper 141] of network 141 to theiright to app y a positive signal on rudder amplifiers i3, i3 resulting in the operation of the left rudder. Network 141 also applies a signal to the aileron network and thus to amplifiers 2G3, 1263' resulting inthe raising of the left elevon and lowering of the right elevon.

Since the disturbance is transient in nature and since the motor 293 slowly drives wiper 291, the network 284 will not supply-any appreciable voltage. Under the applied eievons the craft banks which is sensed by the vertical gyro 333. Gyro 363 operates wiper 26'! of network 250 to supply a signal to limit the amount of the bank; operates wiper '46 of network 41! to return the left rudder toward normal; and operates wiper 3130f network 316 to apply up elevon. As the craft as thus banked turns toward the desired heading, the directional gyro operated wipers move toward normal position and the bank decreases as the desired heading is approached. The rate gyro Ill operates Wiper 3'1 alternately to check deviation due to the transient disturbance and to damp the tendency of the craft to overshoot the desired heading. It appears obvious from the above that left deviations are similarly corrected. Deviations about the pitch axis are corrected by vertical gyro 333 which operates wiper 360 in one or the other direction depending on the deviation. By the above four operations the aircraft is stabilized while the function selector is in the number 2 position.

Function selector No. 3 position In the number 3 position of the function selector, the aircraft is automatically stabilized in flight but the formation stick 511 may be operated to change the attitude of the craft about the turn, roll, and pitch axes. In the number 3 position, contact arm 490 of the sixth switch section engages contact 493 and the circuit through the primaries 184 of the formation stick potentiometers 183, 33?, and 4110 is completed.

The circuit for energizing resistor 312 of the aileron turn control trimmer potentiometer 313 now extends from the right end of resistor 312 through lead 314, through the turn control aileron potentiometer, lead 323, wiper arm 413, contact 472 of the fourth section, contact 462 of the third section, arm 4611, lead 331, the formation stick banking potentiometer 331 to ground and to the left end of resistor 312. The formation stick banking network 331 is thus included in the cirzanlit for applying a voltage drop across resistor The circuit for energizing resistor 13B of the turn control rudder trim potentiometer extends from the right end of resistor 138, through lead 160, turn control rudder potentiometer 162, lead 115, the formation stick rudder network 183, lead 188, lead 189, switch arm 450, contact 451, lead 131, lead 132. and lead 308 to the left end of resistor I38. It is seen that the circuit which now supplies a voltage drop across resistor I38 of the rudder turn control trim potentiometer by-passes resistor 458. Resistor 458 and resistor I38 previously constituted a voltage divider. Now resistor I 38 alone is the voltage divider. The voltage drop across resistor I38 is now increased over that obtained when resistor 458 was in series with it. In other words at this time the rudder turn control trimmer potentiometer comprising wiper I31 and resistor I38 provide a course control signal for the control circuits of amplifiers I3, I3.

The aircraft may now fiy under the stabilizing effects of the directional gyro and the vertical gyro to maintain the aircraft on a desired heading and in level flight laterally and longitudinally and to maintain unyawed flight attitudes.

If the pilot wishes to change the heading of the aircraft he may operate the formation stick 5 in a lateral direction or in the plane of the drawing. The formation stick 5 with member 5I5 will rock about the axis of shaft 5I6. Theswitch arm 530 will engage contacts 53I or 532 depending upon the direction in which the stick 5II is moved. It is immaterial whether arm 530 engages contact 53I or contact 532 since the effect is the same. The engagement of arm 530 with contact 53I closes a circuit from battery 486, lead 503, contact 50I in the seventh section, arm 500, lead 502, arm 530, contact 53 I, or 532, lead 550, erection cutout coil 55I to ground, and to the grounded side of battery 486. The energization of coil 55I operates the erection cutout system to prevent false erection about the roll axis in the vertical flight gyro 363 as stated.

At the same time a circuit extends from battery 488, lead 503, contact 50I, arm *500, lead 502, arm 530, contact 53I or 532, lead 540, contact 605, arm 503, lead 801, coil 608, to ground, and to the grounded side of battery 486. The energization of coil 608 operates the directional arm lock for the directional gyro I55 as disclosed in aforementioned application 441,989 to prevent the transmission of movement to wiper I40 of network MI and to prevent other operative movement from directional gyro to be transmitted to other elements of the system.

We may assume that the pilot wishes to turn the aircraft to the right from its desired or pres ent heading. The pilot moves the stick 5II to the right and thereby engages switch arm 530 with contact 53I to operate the directional arm lock coil 688 and erection coil 55! as described.

The right hand terminals of the secondary wind-,

ings of the various impedance networks and potentiometers are considered positive with respect to the left ends in the particular half cycle under consideration. The formation stick 5 when moved to the right displaces wiper I81 of the formation stick rudder network I83 and the wiper 338 of the formation stick aileron network 331 to the right from their respective center taps I18 and 332.

Wiper I81 is positive with respect to its center tap I18. The center tap I18 is connected through lead I15, the turn control rudder network I63, lead I60 to the right end of resistor I38. The wiper I81 is connected through lead I 88. lead I89, switch arm 450 of the second section, contact 45I, lead IBI, lead I92, lead 308 to the left end of resistor I38. positive with respect to the right end, and the left end of resistor I38 is positive with respect to wiper I 31. The negative potential of wiper I31 The left end of resistor I38 is therefore is applied to amplifier I3 and to amplifier I3: The left end of resistor I38 is connected through network I4I, lead I50 to ground and to the grounded sides of amplifiers I3 and I3. The amplifier I3 efiects the operation of servomotor I2 which operates the right rudder. The drag on the right wing is now increased.

Wiper 338 of the formation stick aileron network 331 is now positive with respect to center tap 332. Wiper 338 through its ground connection is extended to the grounded side of resistor 3 I2 of the aileron turn control trim potentiometer 3I3. The center tap 332 is connected through lead 33I, switch arm 460 of the third section in the function selector, contact 462, contact 412, arm 410 in the fourth section, lead 320, through the aileron turn control network 322, lea-d 3I4 to the right end of resistor 3I2. The left end of resistor 3I2 is positive with respect to the right scribed to amplifier 203 and to amplifier 203'.-

The negative signal on amplifier 203 causes it to operate and through servomotor 202 effects the lowering of the left elevon. The servomotor 202 also displaces the wiper 2I5 of network 2I0 to the right until the voltage between wiper 22I and the lower end of resistor 220 is equal and opposite to that between wiper 3 of potentiometer 3I3 and the left end of resistor 3I2. At this time the control circuit for amplifier 203 is in balance and the amplifier 283 stops operating.

The amplifier 203' responds to the negative signal and causes servom0tor 202' to raise the right elevon. The servomotor 202' moves wiper 2 I 5 of network 2 I 0 to the right until the voltage between wiper 22! and the lower end of resistor 220 is equal and opposite to that between wiper 3i I and the grounded side of resistor 3 I 2. At this 315 of upelevator network 310, and wiper'48 of rudder network 40;

The positioning of wiper 48 to the right raises its potential with respect to center tap 48 and wiper 50 is now positive with respect to the lower end of resistor 48.

to the amplifier circuits from resistor I38. The circuit of amplifier I3 is therefore positive at this time due to the excessof positive voltages over negative voltages. The amplifier I3 causes its servomotor I2 to reverse on this positive signal and moves the operated right rudder back toward the closed position. Since the positive voltage from network 40 may not be in excess of the negative voltage drop across resistor I38, the control circuit for amplifier I3 does not have a positive unbalance and therefore the servomotor I2 is not operated.

The movement of wiper 316 in the network 310 is to the right and raises its potential with respect to center tap 311 of resistor 31I. 315 is connected to the left end of resistor 225 as described. The right end of the resistor is con- The positive voltage from' network 40 opposes the negative voltage applied Wiper nected to ground through the aileron controlv signal circuit. The center tap 3?? of network 378 is connected to the right end of resistor 225. The left end of resistor 225 forms, a junction with. the right end of resistor 225 to complete the circuit. The left end, of resistor 225' like the right end of resistor 225 is also connected to ground through the amplifier control circuit effecting aileron operation. The left end of resistor 225 is positive with respect to its right. end and is connected as described to amplifier. 283. The amplifier 233 responds to the positive signal applied to it and causes the servomotor 202 to raise the left elevon. The wiper H is also positioned by the servomotor 282 toward the left to balance the. control circuit of amplifier 283. The right end of resistor 225 which is negative with respect. to the left end is connected as stated to input, lead 298 of amplifier 29.3. The left end of resistor 225 is connected through lead 227 to a portion of the controlcircuit for amplifier 263' which effects aileron control. This circuit continues from the grounded side of this aileron; control circuit to the grounded side of lead. 287. The amplifier 203' receives a negative signal. at this time and raises the right elevon. The wiper 2E5 is moved by servomotor 202' toward the left to balance the control circuit of amplifier 293'. Thus up elevator action of the elevons is automatically applied. while the craft is turning to offset the tendency to lose altitude in a turn.

The movement of wiper of network 2% by vertical gyro 353 in a right bank is to the right and therefore causes the wiper 2%? to be positive with respect to wiper Zll of network 2633. Wiper 26'! is connected as described to amplifiers 263, 263. Wiper 2H is connected to ground and to the grounded sides of amplifiers 263, 203'. The positive, signal on. amplifier 253 causes the amplifier 2&3 through servomotor 2&2 to raise the left. elevon from its lowered position.

The amplifier 2533 in response to the positive signal causes the servomotor 202' to lower the raised right elevon.

The net effect on the position of the elevons due to the aileron and elevator signals for the amplifier as obtained from the operation of the vertical flight gyro 3'63 is such as to leave both elevons in a slightly raised position but the plane is in its selectedbanked position.

When the aircraft approaches the desired heading, the pilot moves the formation stick 5 back to normal position and therefore moves the wipers l8; set back to the center position of their resistors, ill] and 333. The movement of wiper [8? back to center tap I13 removes the voltage drop across resistor I38 of the rudder turn control trimmer potentiometer. This decreases the negative voltage supplied to the con trol circuits of amplifiers I 3, it. The voltage to the control circuits of amplifiers l3, l3 has a negative voltage decrease. The control circuit of amplifier I? therefore has a positive unbalance and the amplifier 13 causes the servomotor l2- to move the left rudder. toward an open position. The servomotor 12 also moves wiper 21 towards the left to balance the control circuit of amplifier l3.

Since the wiper 338 of the formation stick aileron potentiometer 33! is now at the center tap 332, no potential drop will appear across trimmer resistor Eli. The control circuits for amplifiers 203, 293' will now be provided with a positive unbalanced voltage. The amplifier 25.3 in response. to the. positive'signal causes the servomotor 202 to raise the left elevon. The am.- plifier 223' in response to the positive signal on its control circuit causes the servomotor 232' to lower the right elevon.

The raising of the left elevon and the lowering of the right. causes the aircraft to lessen its tilt about the roll axis. In other words the aircraft is moved from the right depressed angular position counterclockwise toward a level position,

The vertical flight gyro 3B3 responds to the change in the position of the aircraft about the roll axis. The vertical night gyro now moves wiper 26'! of network 259 toward the left, moves wiper 3T6 toward the left and moves wiper 4B of network 48 toward the left.

The movement of wiper d6 toward the left re sults in a lowering of the positive voltage applied to the control circuit. of amplifier l3. The amphfier circuit therefore in effect. receives a negative voltage. In response to this negative volt' age the amplifier I3 causestheservomotor I2 to move the left rudder toward the closed position.

In the elevator control of the elevons, the movement of wiper. 3J5 toward its center causes the amplifier 203 to receive a negative signal in its control circuit. In response to this negative signal the amplifier 203 causes the servomotor 202 to lower its left elevon.

Theamplifier 203' has the negative voltage in its. control circuit decreased andin effect has an excess of positive voltage applied thereto. Therefore the amplifier 293' in response to the positive. signal causes the servomotor 202 to lower the right. elevon.

In the aileron control. circuits for the ampli fiers 203, 203, the movement of wiper 26'! toward the left or toward the center of resistor 25! do. creases. thepositive signal in the control circuits of the amplifiers 2G3, 203'. The amplifier circuits. are. now provided with a negative signal which causes the amplifier 203 to effect rotation of servomotor 2B2 whereby the raised. left elevon islowered. Onthe-other hand. the, amplifier 203 in, response to, the negative signal causes the servomotor 202 to raise the lowered right elevon.

The action is continuous, as the wipers I81 and 338 are manually moved toward their center taps I13 and 332, the aileron control circuits for the amplifiers 203, 2.03 tend to. effect a raising of the left elevon and: a lowering of the right elevon. This positioning of the elevons tends to decrease the angular tilt of the aircraft, and the vertical gyro. in. response to the lessening of the tilt pro.- vides. a signal from network. 260 which tends to lower the left elevon and raise the right elevon.

The vertical flight gyro 353 in its control of network 310 of the up elevator control circuit tends to lower both the left and right elevon.

The movement of wiper 46 of the compensating network All by gyro 363 toward the left from its right position causes the. amplifier l3 to operate motor 12 so that the operated left rudder is moved toward the unoperated position. When the aircraft reaches the desired heading the control networks 2.60, 40, 370, the formation stick rudder network 183, and the formation stick aileron network 33'! are inbalanced condition. At this time also the circuits through the erection cutout coil 55! and the. directional arm lock coil 608 are open. The aircraft now may be automatically stabilized on the new heading in which it has been placed through the operation of the formation stick 5! I.

It is also apparent that should the pilot desire he may by operating the formation stick I perpendicular to the plane of the drawing cause the displacement of the wiper 409 of the elevator network 400. The network 400 is in series with the networks 35L 310 of the elevator control network for amplifiers 203, 203'. The pilot may therefore apply either additional up elevator or decrease the amount of up elevator which is automatically applied.

Function selector No. 1 position The type of operation provided when the function selector is in the No. 1 position is often referred to as servo boost. In the No. 1 position the directional gyro and the vertical flight gyro are render ineffective to control the input circuits of the various amplifiers. Control of the amplifier circuits is obtained by manual control only.

With the function selector in the Number 1 position, the first, second, third, fourth and seventh sections of the formation stick function selector have their respective switch arms engaging inoperative contacts. In the fifth section the battery 486 is connected through lead 485, contact 48I, switch arm 480, lead 482, through coil Bill to ground and to the ground side of the battery 486 whereby a circuit is completed to the coil GM and it operates toraise the switch arms 603, 6H, 6H and 630. In the sixth section of the function selector the switch arm 498 completes a circuit for the primaries I84 of the formation stick of the potentiometers I83, 331, and 400.

The operation of coil 60] causes switch arm 603 to contact the in contact 604. A circuit is now completed from battery 486, lead 485, contact 48L switch arm 480, lead 482, lead 609, in contact 604, switch arm 503, lead 601, directional arm lock coil 608 to ground and to ground side of battery 486. The directional arm lock coil 608 is therefore energized and operates the directional arm lock to prevent the transmission of movement from the directional gyro to elements of the flight control system normally operated thereby. A circuit is also completed from lead 801, lead 648, through coil 649 to ground and to the ground side of battery 486 whereby the coil 649 moves switch arm 302 from engagement with contact 303 into engagement with contact 304. Amplifier 291 is now isolated from network 284 and aileron trimmer potentiometer resistor 3I2 otherwise if recentering switch 654 is operated while the turn control knob I or the formation stick 5 is operated, motor 296 would not move wiper 29I to center of resistor 285 but to some other position.

The engagement of switch arm 6II with contact 6 I2 interrupts out any signal that might be provided in aileron control network 260 through the operation of the vertical flight gyro. Any voltage that might develop between wiper 261 of network 260 and wiper 213 whose resistor 212 is in parallel with resistor 26I is applied across through the high resistor H4. The vertical flight gyro will now be unable to provide any signal in network 260 controlling the aileron operation of the amplifiers 203, 203.

The engagement of switch arm 8I1 with contact EIS interrupts any signal that might be derived from networks I, 310 which are intermediate the wipers 366 and 316. The wipers 365 and 318 are now the output members for the series connected networks 35I and 310. If these wipers 366 and 316 are directly connected the impedance networks 35l and 310 will not have any output. The actual voltage between wipers 386 and 316 is now applied across high value resistor 629 which is not in series with the effective bridge circuit. The vertical flight gyro will therefore not effect any voltage output from networks 35I and 310 which will control the operation of the control circuits for amplifiers 203, 203 for efiecting elevator action of the elevons.

The engagement of switch arm 630with contact 63I connects the junction of leads 35, 35 in the rudder control circuit with the wiper I31 of the rudder turn control trimmer potentiometer. The wiper I3? and the junction of leads 35, 35 form the output elements of networks 40, 60, and 80. If these outputs are therefore connected together the impedance networks will have no output that will control the operation of amplifiers I3, I3.

The directional arm lock coil 608 had been energized by the engagement of switch arm 603 with contact 604 therefore the impedance network I45 will have no output to control the operation of the rudder amplifiers I3, I3.

Assume now that it be desired to turn the aircraft to the right. The formation stick 5II will be tilted to the right in the figure and through the operating connection 528 will displace wipers I81 of the formation stick rudder network I83 to the right and the wiper 338 in the formation stick banding network 331 to the right from their respective center taps I18 and 332. As in previous cases, the right end of the various secondary windings will be considered positive with respect to the left end in the particular half cycle under consideration. Movement of wiper I81 of the potentiometer I83 to the right raises its potential with respect to center tap I18. Center tap I18 is connected through lead N5. the turn control rudder potentiometer I82, lead I60, to the right end of resistor I38. Wiper I81 is connected through lead I88, resistor 458, lead I92, lead 308, to the left end of resistor I38 of the rudder turn control trimmer potentiometer. The left end of resistor I38 is now positive with respect to the wiper I31 which engages the resistor I38. The left end of resistor I38 is connected to ground through network MI and lead I50. The wiper I3! is connected through lead 635, contact 63L- switch arm 630, lead 334, to the junction of leads 35, 35' from where its potential is transmitted on the one hand through network 20 to amplifier I3 and on the other'hand through network 20 to amplifier I3. With the networks 20, 20 pre viously in balanced condition, the application of a negative signal to each amplifier I3, I3

causes only the operation of servomotor I2. The

is at a positive potential with respect to center Wiper 338 is connected to ground andtap 332. through the ground connection of the turn control aileron trimmer potentiometer resistor 3I2 is connected to the left end of resistor 3I2. The center tap 332 is connected through lead 33I, re-

sistor 330, lead 320, through the turn control is negative with. respect to the left end therefore wiper .3I I is negative with respect to the left end or grounded end of resistor 3I2. The positive left end of resistor 3I2 is connected through ground-to the ground terminals 201, 201 of amplifiers 293, 203'. The wiper 3 is connected through lead 3I0, network 284, lead 280, network 260, wiper 273, contact BIZ, switch arm 6! I, lead 248, network 230, lead 221, to the junction of resistors 225, 225 from which the control circuit on the one hand is transmitted through lead 224, network 2I0 to amplifier 203 and on the other hand through resistor 225, lead 220', network 2l0' to amplifier 203'. The amplifiers 203 and 203 now have a negative signal applied to their control circuits. In response to the negative control circuit the amplifier 203 causes the servomotor 202 to lower the left elevon. The amplifier 203' in response to the negative signal raises the right elevon. In response to the lower left elevon and the raising of the right elevon, the aircraft banks toward the right.

If it is necessary to operate the elevons in elevator fashion to maintain the altitude of the craft during this manually initiated turn, the pilot pulls the formation stick II toward him. This movement causes the wiper 409 to be displaced to the right of center tap 403 in the formation stick elevator network 400. Wiper 499 is now positive with respect to center tap 403. The potential between the Wiper 409 and center tap 403 is applied to amplifiers 203, 203' as described. The amplifier 203 therefore receives a positive signal which causes the servomotor 202 to raise the left elevon. The amplifier 203 now has a negative signal applied thereto which causes it to effect rotation of servomotor 202 whereby the right elevon is raised. When the craft has at tained the desired angle of bank, the pilot returns the formation stick to normal lateral position, resulting in the return of the control surfaces to normal position for lateral control.

The aircraft now proceeds in the right turn toward the desired heading. When the aircraft has approached the desired heading, the pilot moves the formation stick 5 to the left of its center position laterally and longitudinally. When the wiper I8! is moved toward the left from its normal position, the voltage drop across re sistor I38 in the turn control trimmer potentiometer for the rudder is in the opposite direction. A positive signal is now imposed on amplifler I3 which causes it to operate and move the left rudder toward open position. At the same time the wiper 21 is moved toward the left so that the voltage drop between wiper 34 and the lower end of resistor 33 is equal and opposite to that between the wiper I37 and the left end of resistor I38.

The movement of the wiper 338 of the formation stick banking network 331' to the left from normal reverses the voltage between wiper 338 and center tap 332. The voltage between wiper 3| I and the left end of resistor 3I2 now reverses. The positive voltage applied to the amplifiers 203, 203' operates the amplifier 203 to cause the servomotor 202 to raise the left elevon. The amplifier 203' in response to the positive signal lowers the right elevon.

In the formation stick. elevator network 400, the movement of wiper 409 toward the center tap 403 decreases the voltage between them. Ampliher 203 in effect receives a negative signal. This negative signal causes the amplifier 203 to effect rotation of servomotor 202 whereby the left elevon is lowered. Amplifier 203 in effect re- 32 ceives a positive voltage. In response to thepositive signal on its control circuit, amplifier 203" lowers the right elevon.

Through the above operation, the aircraft is manually controlled to change the heading thereof, the servomotors acting merely as power boost or power amplifying devices,

Function selector No. 4 position In the No. 4 position, the formation stick rudder and aileron networks I83, 331 are rendered ineffective. In the number four position of the function selector, switch arm MI in the top section engages contact 443. A circuit is now completed from center tap 503 of the formation stick elevator network 000, lead 408, resistor 394, lead 49?, contact 043, switch arm MI, lead 442, lead M2 to wiper arm 009. The resistor 394 now functions as a voltage divider for the potential derived from network 400. A portion of the voltage across the dividing resistor 394 is applied to resistors 225, 225 in a circuit extending from the right end of resistor 394, lead 401, contact 443, arm 44!, lead 042, lead 413 through the left end of resistor 225, resistor 225', lead 350, network 35!, lead 368, network 370, lead 393, contact 6I9, switch arm 0H, lead 393, to the tap M0 on resistor 394.

In the second section of the function selector the engagement of switch arm 450 with contact 032 renders ineffective for formation stick rudder potentiometer I33 by directly connecting the center tap I'IS through lead 454, contact 452, switch arm 053, lead I89, lead I88 to wiper I81.

In the third section of the function selector, the engagement of wiper 490 with contact 663 renders the formation stick bank network 331 ineffective since the center tap 332 and the wiper 330 thereof are directly connected through a circuit extending from center tap 332, lead 33I, switch arm 030, contact 463 to ground and to the grounded wiper 33B. No potential difference therefore can develop between the wiper 338' and center tap 332.

The aircraft in the number four position of the function selector is automatically stabilized in flight but the formation stick is effective to change the altitude of the aircraft about thepitch axis.

As the. aircraft is flying under the stabilizing. effects of the automatic control features and should the pilot wish to increase his altitude, he operates the formation stick 5 and pulls it toward him. Through the operative connection. SIS the wiper 409 is displaced to the right of its center tap 403. A voltage which now' exists between wiper 409 and center tap 403 is applied across the voltage dividing resistor 390. portion of this voltage utilized in the control of the elevons is that between center tap 410 of resistor 394 and the right endof resistor 394. The right end of resistor 394 is positive with respect to the center tap M0. The left end of resistor 225 is'positive with respect to its right end which is connected to ground, The amplifier 203 responds to a positive signal and raises the left elevon and moves wiper 2 I5 to the left to balance.

The right end of resistor 225' is negative with respect to its left end which is connected to ground. The amplifier 203' receives a negative signal in its control circuit and operates itsservomotor 202 to raise the right elevon and moves wiper 2I5' to right. The vertical gyr responds to the change of the plane about the pitch axis and moves wiper 3 to the left. This opposes voltages from network 400 so that the voltage from The- 33 the elevator network is balanced by the voltages from the servo balance networks and the vertical gyro pitch axis network 35!.

When the desired altitude has been reached, the pilot moves the formation stick back to center which moves wiper 409 back to center tap 403. The voltage drop across resistors 225 and 225' is now in the opposite direction. The drop in the voltage across resistor 225 in effect causes a negative signal to be applied to amplifier 293 which operates and causes servomotor 202 to lower the left elevon and move wiper 2 I5 to the right. The voltage drop across resistor 225' in effect applies a positive signal to amplifier 203. Amplifier 203' in response to the positive signal causes the servomotor 202' to lower the right elevon and position wiper M5 to left. As the plane levels 011, the vertical gyro 363 moves wiper 3B0 toward center. The aircraft now flies at the new altitude selected by the pilot. The networks controlled by the turn control knob I10, the directional gyro I55, vertical gyro 353, and yaw vane H1 continue to be effective.

Conclusion The operation of the flight control system for the four positions of the function selector have now been particularly described. It has been pointed out how the aircraft may be automatically stabilized in flight but yet be made subject to alternative manual control as desired. It was explained further how the control surfaces may compensate for conditions which make the craft yaw or tilt.

Having described a preferred embodiment of my invention, but realizing that changes in the particular details described may be made without departing from the spirit of my invention, I do not wish to confine my invention to the specific structure described but only as defined by the appended claims.

What is claimed as new is:

1. Flight control apparatus for an aircraft having two control surfaces, motor means for each control surface; control means for each motor means; attitude signal generating means responsive to the movement about one axis and connected to said control means to effect operation of said motor means whereby said control surfaces are moved together in the same direction to stabilize said craft about said one axis; attitude signal generating means responsive to the movement about another axis and connected to said control means to effect operation of said motor means whereby said control surfaces are moved in Opposite directions to stabilize said craft about said other axis; manual signal generating means connected to said control means to effect operation of said motor means to obtain same or opposite movement of said control surfaces to effect attitude change about both axes; and selector means to render both said attitude responsive signal generating means ineffective to control said control means and for rendering said manual signal generating means effective, whereby opposition to said manual changes of craft attitude by said stabilizing means is prevented.

2. A control system for an aircraft having two control surfaces operable in the same or opposite directions and thus adapted to change the angular position of the aircraft about two axes, and including: control means for operating said control surfaces; a first controller responsive to the angular position of said aircraft about one axis and associated with said control means; a second controller responsive to the angular position of said aircraft about another axis and associated with said control means; a first and a second manually operable controller associated with said control means; the first manually operable controller and a responsively operable controller bee ing so associated with said control means as to cause a positioning of said control surfaces in the same direction, and said second manually operable controller and said other responsively operable controller being associated with said control means as to cause the operation of the control surfaces in opposite directions; and means including switching means associated with said control means and adapted in one position of said switch to disconnect said manually operable controllers from said control means whereby they are ineffective to control said control surfaces and whereby said responsively operated controllers tend to maintain said aircraft in a given angular position about said axes, or in another position of said switch to connect said manually operable controllers with said control means to render them effective tomodify the action of said responsively operated controllers, whereby said responsively operable controllers are effective to maintain said aircraft in angular position about said axes determined by said manually operable controllers.

3. A control apparatus for an aircraft having two control surfaces adapted to change the angular position of the aircraft about two axes, and including: motor means operable to position said control surfaces; means responsive to the angular position of said aircraft about said axes; a first and second variable impedance controlled by said responsive means; a first and second manually controlled impedance; a follow up type control system connected to said motor means and in cluding said first and second variable impedances and said manually operated impedances, said control system being effective to control the opera-, tion of said motor means in accordance with signals provided by said first variable impedance and by one manually operated impedance whereby said control surfaces are operated together in the same direction, and said control system being effective to control the operation of said motor means in accordance with signals provided by said second variable impedance and by the second manually operated impedance whereby said control surfaces are operated in opposite directions, and switching means adapted to render said manual control means ineffective and said first and second variable impedances effective to control the operation of said motor in such a manner as to tend to maintain said aircraft in a predetere mined angular position about said axes, or to' render said manually operated impedances elfective to produce signals in accordance with the operation of said impedances, and said first and second variable impedances effective to produce signals tending to maintain said aircraft in a given angular position about said axes, whereby said manually operated impedances may be op erated to modify the effect of said first and second variable impedances and thereby change the angular position which said first and second variable impedances will tend to maintain. f

4. Control apparatus for an aircraft having two control surfaces adapted to change the angular position of the aircraft about two axes, and including: control means associated with said: control surfaces, 2. first controller responsive to. the angular position of said aircraft about one:

axis; aisecond controller responsive to the angular position of said aircraft about a second axis, bothsaid responsively operable controllers being associated with said control means; a first and a second manually operated controller; the firstresponsivecontroller and the first manually operated controller being so associated with said controlmeans as to cause the operation of said surfaces in the same direction, and said second responsive controller and said second manually operated controller being so associated with said control means asto cause the operation of said control surfaces in opposite directions; means including switching means operable in one position to connect both said responsively operated controllers and said manually operated controllers to said control means to render them effective to control said control surfaces so as to maintain said aircraft in a predetermined angular position about said axes with said manually operated controllers effective to vary said predetermined angle or in another position to dlsconnect said responsively operated controllers fromsaid control means to render them inefiective-to control the operation of said control surfaces, whereby said manually operated controllers areefiective to control the position of said control surfaces.

5. Control apparatus for an aircraft having two control surfaces adapted to change the angular positions of the aircraft about two axes and including: motor means-operable to position said control surfaces; a first controller responsive to the angular position of said aircraft about one axis, a second'controller responsive to the angular position of said aircraft about another axis, afirst anda second manually operated'controller; control means including said manually operated controllers andsaid responsively operated controllers, and connected to said motor meansto control the operation thereof in accordance'with signals provided by said controllers, the first'responsive controller and the first'manually operated controller controlling said motor means to operate the control surfaces in the same direction and the second responsively operated-controller and the second manually operated controller controlling the'mot'or means to position the control surfaces in opposite directions; and means including switching'means associated with said control means and'adapted in one position-of said switch to render both "responsively operated controllers and both manually operated controllers effecti've'to control the operation of said motor'means so as 'to tend to maintain said aircraft in a predetermined angular position about said axis, which predetermined angular positions may be varied by operation of said manually operated controllers, or in another position of said switch to render said responsively operated controllers ineffective and reduce the effective magnitude of the signals produced by said manually operated controllers to operate said-motor means.

6. Control apparatus for an aircraft having two controlsurfaces adapted to change the angular positions of the aircraft about two axes and including: motor means operable to position said control surfaces, means responsive to the angular position of said aircraft about said axes; a flrst and-second variable impedance controlled by said responsive means; a first and second manually controlled variable impedance; two control circuits including said responsive variable impedances and said manually controlled variable Timp'edanc'es and operable to control the operation of said motor means,said first IBSIJOTP sive variable impedance and said first manually operated impedance being connected in one circuit so as to providesignals causing the operation of said motor-means whereby said control surfaces are moved together in'the same direction; and said second responsive variable impedance and said second manually operated impedance being connected in the second circuit so as to provide signals causing the-operation of said motor means to position the control surfaces in opposite directions; and switching means adapted to render said responsive impedances ineffective and said manually controlled variable impedances effective whereby said manually controlled means are effective to control the oper: ation of said control surfaces independently of the angular positions of said aircraft about the two axes, or to render said first and second responsive impedance means and said manually controlled variable impedances effective to cause the operation of said motor means so as to tend to maintain said aircraft in given angular positions about said axes which positions may be modified by the operation of said manually controlled impedances.

7. A control apparatus for an'aircrafthaving two control surfaces adapted to change'the position of the aircraft about two axes and including: motor means operable'to position said control surfaces; means responsive to the angular position of said aircraft about said axes; a first and a second variable resistor controlled by said responsive means; a'first and a second manually controlled variable resistor; rebalancing variable resistors controlled by said'motor means; a'first controlled circuit of the rebalancing type operable to control the operation of said motor means to cause the positioning of said control surfaces in the same direction and including said first responsive variable resistor, said first manually controlled variable resistor, and said 'rebalancing resistors, and'a second control circuit of the rebalancing type operable to control'the operation of said motor means to cause said control surfaces to move in opposite directions and including said second responsive variable resistor, said second manually controlled variable resistor, and said rebalancing resistors, said firstand second responsive resistors providingsignals which tend to operate said motor means so as to maintain said aircraft in predetermined angular positions about its axes, and said manually controlled resistors providingsignals which'normally tend to operate said motor means; and switching means operable to render said manually controlled resistors inelfective and said first and second responsive resistors effective to control the operation of said motor means, or to render said manually operated resistors effective to control the operation of said motor means while effectively disconnecting said first and sec-' ond responsive variable resistors from said control circuits to render them ineffectiveto control said motor means.

8. A control apparatus for an aircraft having" two control surfaces adapted to change the angular position of the aircraft about'two axes'and including: motor means operable to position said control surfaces; means responsive to the angular position of said aircraft about said axes; a first control device operated by said responsive meansin accordance with the position of theair-' craft about one'axis; asecondcontrol device 012-" 

